The regulated secretion of neurotransmitters from neural cells proceeds by the Ca2' activation of fusion of secretory granules with the plasma membrane. The exocytotic membrane fusion process requires ATP and our previous studies identified lipid phosphorylation and the synthesis of phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2) as a key biochemical reaction in regulated secretion for which ATP is required. Conventional immunofluorescence studies with PI(4,5)P2-specific monoclonal antibodies indicated a remarkable localization of the ATP-dependent PI(4,5)P2 synthesis to secretory granules as assessed in colocalization studies with antibodies to granule-specific constituents. We wish to extend these localization studies to a higher resolution provided by confocal microscopy.